Add merge functionality

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.19-alpine as builder
+FROM golang:1.20-alpine as builder
 
 WORKDIR /build
 

README.md

@@ -23,6 +23,14 @@ Replaces existing .gitignore based on given language in defined location (either
 ignoreinit replace <language> <location>
 ```
 
+### Merge existing gitignore
+
+Merges a gitignore for given language into existing .gitignore in defined location (either relative or absolute).
+
+```bash
+ignoreinit merge <language> <location>
+```
+
 ## Build from source
 
 ```bash

main.go

@@ -5,7 +5,7 @@ import (
 	"github.com/loupeznik/ignoreinit/src"
 )
 
-const version = "1.0.2"
+const version = "1.1.0"
 
 func main() {
 	flags := src.Flags{}

snap/snapcraft.yaml

@@ -1,6 +1,6 @@
 name: ignoreinit
 base: core20
-version: '1.0.3'
+version: '1.1.0'
 summary: A tool for creating .gitignore files from the command line
 license: MIT
 contact: contact@dzarsky.eu

src/flags.go

@@ -9,4 +9,7 @@ type Flags struct {
 	Replace struct {
 		Settings bool `settings:"true" allow-unknown-arg:"true"`
 	} `command:"replace" description:"Replace current .gitignore - use ignoreinit replace <language> <location>" nonempty:"true"`
+	Merge struct {
+		Settings bool `settings:"true" allow-unknown-arg:"true"`
+	} `command:"merge" description:"Merge a new gitignore into current .gitignore - use ignoreinit merge <language> <location>" nonempty:"true"`
 }

src/handlers.go

@@ -16,6 +16,7 @@ import (
 const (
 	fncInit    = "Init"
 	fncReplace = "Replace"
+	fncMerge   = "Merge"
 	gitOwner   = "github"
 	gitRepo    = "gitignore"
 )
@@ -33,7 +34,7 @@ func InitHandlers() {
 			return nil
 		}
 
-		err = getIgnore(language, location, true)
+		err = getIgnore(language, location, true, false)
 
 		if err != nil {
 			return err
@@ -56,7 +57,7 @@ func InitHandlers() {
 			return nil
 		}
 
-		err = getIgnore(language, location, false)
+		err = getIgnore(language, location, false, false)
 
 		if err != nil {
 			return err
@@ -66,6 +67,29 @@ func InitHandlers() {
 
 		return nil
 	})
+
+	gocmd.HandleFlag(fncMerge, func(cmd *gocmd.Cmd, args []string) error {
+		language, location, err := handleParams(cmd.FlagArgs(fncMerge)[1:])
+
+		if err != nil {
+			return err
+		}
+
+		if _, err := os.Stat(path.Join(location, ".gitignore")); errors.Is(err, os.ErrNotExist) {
+			fmt.Printf(".gitignore does not exist in %s\n", location)
+			return nil
+		}
+
+		err = getIgnore(language, location, false, true)
+
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("Merged .gitignore in %s\n", location)
+
+		return nil
+	})
 }
 
 func handleParams(params []string) (string, string, error) {
@@ -80,7 +104,7 @@ func handleParams(params []string) (string, string, error) {
 	return params[0], params[1], nil
 }
 
-func getIgnore(language string, location string, isNew bool) error {
+func getIgnore(language string, location string, isNew bool, isMerge bool) error {
 	client := github.NewClient(nil)
 	ctx := context.Background()
 	options := &github.RepositoryContentGetOptions{}
@@ -124,6 +148,24 @@ func getIgnore(language string, location string, isNew bool) error {
 	var file *os.File
 	fullPath := path.Join(location, ".gitignore")
 
+	if isMerge {
+		file, err = os.OpenFile(fullPath, os.O_RDWR|os.O_APPEND, 0755)
+
+		if err != nil {
+			return err
+		}
+
+		defer file.Close()
+
+		_, err = file.Write(bytes)
+
+		if err != nil {
+			return err
+		}
+
+		return nil
+	}
+
 	if isNew {
 		file, err = os.Create(fullPath)
 	} else {